enforce global_constant name should be a string
enforce global_constant name should be a string

Reviewed By: kennyhorror

Differential Revision: D6880114

fbshipit-source-id: 2c9bd27b01cedb469f19843163b04a613fda5904

Yangqing/caffe2,Yangqing/caffe2,xzturn/caffe2,caffe2/caffe2,Yangqing/caffe2,xzturn/caffe2,Yangqing/caffe2,Yangqing/caffe2,xzturn/caffe2,xzturn/caffe2,xzturn/caffe2